CN103026406A - Device and method for postprocessing decoded multi-channel audio signal or decoded stereo signal - Google Patents

Device and method for postprocessing decoded multi-channel audio signal or decoded stereo signal Download PDF

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CN103026406A
CN103026406A CN201080022195XA CN201080022195A CN103026406A CN 103026406 A CN103026406 A CN 103026406A CN 201080022195X A CN201080022195X A CN 201080022195XA CN 201080022195 A CN201080022195 A CN 201080022195A CN 103026406 A CN103026406 A CN 103026406A
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CN103026406B (en
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大卫·维雷特
郎玥
苗磊
吴文海
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Huawei Technologies Co Ltd
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    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/008—Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L21/00—Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility
    • G10L21/02—Speech enhancement, e.g. noise reduction or echo cancellation
    • G10L21/0316—Speech enhancement, e.g. noise reduction or echo cancellation by changing the amplitude
    • G10L21/0364—Speech enhancement, e.g. noise reduction or echo cancellation by changing the amplitude for improving intelligibility
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/02—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using spectral analysis, e.g. transform vocoders or subband vocoders
    • G10L19/022—Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
    • G10L19/025—Detection of transients or attacks for time/frequency resolution switching

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Abstract

The invention relates to a device and method for postprocessing a decoded multi-channel audio signal or a decoded stereo signal. A device and method for postprocessing a decoded multi-channel audio signal or a decoded stereo signal are provided. The device comprises a receiver (103; 103') for receiving at least one channel signal generated from the decoded downmix signal, a time envelope of the decoded downmix signal and a classification indication indicating a transient type of the at least one channel signal, wherein the classification indication is associated with the at least one channel signal, and a postprocessor (105; 105') for postprocessing the at least one channel signal based on the time envelope of the decoded downmix signal weighted by a respective weighting factor and in dependence of the classification indication.

Description

For the apparatus and method that decode multi-channel audio signal or the stereophonic signal of having decoded are carried out aftertreatment
Technical field
The present invention relates to the aftertreatment with decode multi-channel audio signal and the stereo audio signal of having decoded, the concrete condition that the aftertreatment representative of the stereo audio signal of having decoded is carried out aftertreatment to decoding multi-channel audio signal.
Background technology
In traditional audio coder ﹠ decoder (codec), usually can classify to voice signal, to improve the code efficiency of voice signal.In demoder, can use dissimilar speech processes instruments according to the classification of the voice signal that transmits.
One of them classification is to distinguish normal voice signal and transient speech signal.Transient signal is short signal, and it is very fast to be characterized in that signal power and signal amplitude change.Transient signal is with respect to " normally " signal or non-transient signal, and " normally " signal or non-transient signal refer to that long-term signal and/or signal power and signal amplitude change very little signal.This classification is not only applicable to voice signal, is applicable to general sound signal yet.
For transient signal, a kind of common method is to extract the temporal envelope of input signal in scrambler, then transmits the temporal envelope of extracting and in demoder it is carried out aftertreatment.
For stereophonic signal, this aftertreatment is normally necessary, but inadequate the encode temporal envelope of two sound channels of bit usually.
With reference to quoted passage [1], the low bit rate stereo coding is take the Parametric Representation that extracts and quantize stereo sound image as the basis.Then, these parameters can be used as side information with being transmitted by mixed signal under the monophony of core encoder coding.In demoder, can rebuild stereophonic signal according to mixed signal and side information (that is the stereo parameter that, comprises space [left side and the right side] information of stereophonic signal) under the monophony.
For the stereo coding/decoding device, if mixed signal is classified as transient signal under the monophony, may has the Pre echoes breast in the stereophonic signal that then rebuilds and resemble.Carrying out aftertreatment, can to improve two sound channels all be transient state sound channel or to only have a sound channel be the quality of the signal of transient state sound channel.But for the parameter stereo codec, the temporal envelope of two sound channels of usually can inadequate bit encoding.
According to quoted passage [2] and [3], monophonic input signal is classified as transient signal and normal signal in scrambler.Then, in demoder, according to the classified information of transmitting, can improve quality with the markers composition algorithm.Above-mentioned various algorithm all is applicable to mixed signal under the monophony.
This problem of Bandwidth-Constrained that can be used for signal transmission not only can run into when transmission stereo language signal or sound signal, and be a FAQs that can run into when transmitting multi-channel audio signal, stereo audio coding represents the concrete condition of multi-channel audio coding.
Summary of the invention
The embodiment of the invention provides a kind of detection method and device of multiple-input, multiple-output signal, be used for keeping in the situation of same magnitude at the computation complexity with the Parallel Interference Cancellation method, bit error rate performance is better than the Parallel Interference Cancellation method, and the bit error rate performance that the MIMO signal of contraction carries out demodulation is better than the Parallel Interference Cancellation method.
The purpose of this invention is to provide the coding method of a kind of better low bit rate parametric multi-channel or parameter stereo coding method, in order to reduce Pre-echo artifacts in the transient audio signal in the high bandwidth efficiency mode.
According to first aspect, a kind of device that the stereophonic signal of decoding of being processed by the audio frequency coding with low bit ratio system is carried out aftertreatment of being applicable to is used in suggestion, and wherein said device comprises a receiver and a preprocessor.This device is used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system, and represent the lower mixed signal of stereophonic signal or the lower mixed signal of having decoded.Receiver can be used for receiving the left channel signals of stereophonic signal and right-channel signals, the left channel signals that is just generating from the lower mixed signal of decoding and right-channel signals, the decode classification indication of transient type of the temporal envelope of lower mixed signal and indication stereophonic signal.Preprocessor can be used for according to the temporal envelope of the lower mixed signal of having decoded (being weighted in the mode that depends on the classification indication by corresponding weighting factor) in the middle of left channel signals and the right-channel signals at least one being carried out aftertreatment.
According to classification indication, can determine selectively and will carry out aftertreatment to which or which left channel signals and right-channel signals.The mode of weighting temporal envelope that can be by the lower mixed signal of decoding is carried out aftertreatment, and the lower mixed signal of decoding can be weighted by weighting factor.
If carry out stereo audio coding, lower mixed signal can be described as again mixed signal or monophonic signal under the monophony, and sort signal can generate from left channel signals and right-channel signals in scrambler.Mixed signal can transmit by audio track (but generally being to pass through transmission link) and is transferred to device to carry out aftertreatment under the coding that generates.This device be used to carrying out aftertreatment can be an ingredient of demoder.In addition, a transient state detection model or entity can be arranged in the scrambler, be used for providing indication for aftertreatment for device, be transient signal to indicate lower mixed signal.Particularly, if lower mixed signal is classified as transient signal by the transient state detection model, then can extract the temporal envelope of lower mixed signal and it is transferred to demoder, this demoder can be with described device be used to carrying out aftertreatment.
According to the first form of implementation of first aspect, this device can also be with the determinant that is useful on decision and will carries out aftertreatment to which or which left channel signals and right-channel signals.Determinant can be made decision according to the classification indication of the transient type of indicating stereophonic signal.
The second form of implementation according to first aspect, this device can also be with the determinant that is useful on decision and will carries out aftertreatment to which or which left channel signals and right-channel signals, and this determinant can be made decision according to the decoded classification indication of transient type of lower mixed signal of the classification indication of the transient type of indication stereophonic signal and indication.The classification of the transient type of indication stereophonic signal indicates and indicates the classification indication of the transient type of the lower mixed signal of having decoded to be provided by scrambler.
Except these two classification indications, determinant can also receive and use level difference between sound channel (CLD) and other stereo parameter.CLD and other stereo parameter can be provided by scrambler.
The third form of implementation according to first aspect, this device can also be with the determinant that is useful on decision and will carries out aftertreatment to which or which left channel signals and right-channel signals, this determinant can be made decision according to the classification indication of the transient type of indicating stereophonic signal, and wherein said determinant can determine and will carry out aftertreatment to left channel signals and right-channel signals in the situation of the non-transient type of classification indication indication stereophonic signal.
Therefore, if lower mixed signal is transient signal, and three-dimensional acoustical signal is non-transient signal, and so, left channel signals and right-channel signals can be carried out aftertreatment.If left channel signals and right-channel signals are all carried out aftertreatment, then can use the temporal envelope (being called again the monophony temporal envelope) of the lower mixed signal of having decoded; The lower mixed signal of having decoded is weighted by different weighting factors, and the weighting factor that is used for each sound channel signal is called the weighting factor specific to sound channel signal.
The 4th kind of form of implementation according to first aspect, this device can also be with the determinant that is useful on decision and will carries out aftertreatment to which or which left channel signals and right-channel signals, this determinant can be made decision according to the classification indication of the transient type of indicating stereophonic signal, and wherein said determinant can determine to carry out aftertreatment to which (unique one) left channel signals and right-channel signals in the situation of the non-transient type of classification indication indication stereophonic signal.
The 5th kind of form of implementation according to first aspect, this device can also be with the determinant that is useful on decision and will carries out aftertreatment to which or which left channel signals and right-channel signals, this determinant can be made decision according to the classification indication of the transient type of indicating stereophonic signal, and wherein said determinant can determine and will carry out aftertreatment to one of them signal energy higher left channel signals and right-channel signals in the situation of the non-transient type of classification indication indication stereophonic signal.
The 6th kind of form of implementation according to first aspect, preprocessor can also be with the first aftertreatment entity, and this entity can use the temporal envelope of mixed signal under the decoding that receives (by the first weighting factor weighting) to come left channel signals is carried out aftertreatment.
The 7th kind of form of implementation according to first aspect, preprocessor can also be with the second aftertreatment entity, and this entity can use the temporal envelope of mixed signal under the decoding that receives (by the second weighting factor weighting) to come right-channel signals is carried out aftertreatment.
According to the 8th kind of form of implementation of first aspect, this device can also be with a determinant, the first aftertreatment entity and the second aftertreatment entity.This determinant can determine and will carry out aftertreatment to which or which left channel signals and right-channel signals, can make decision according to the classification indication.The first aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the first weighting factor weighting) to come left channel signals is carried out aftertreatment.The second aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the second weighting factor weighting) to come right-channel signals is carried out aftertreatment.Determinant can be used for controlling the first aftertreatment entity and the second aftertreatment entity.
According to the 9th kind of form of implementation of first aspect, this device can also be with a determinant, the first aftertreatment entity and the second aftertreatment entity.This determinant can determine and will carry out aftertreatment to which or which left channel signals and right-channel signals, can make decision according to the classification indication.The first aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the first weighting factor weighting) to come left channel signals is carried out aftertreatment.The second aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the second weighting factor weighting) to come right-channel signals is carried out aftertreatment.Determinant can be used for according to level difference (CLD) between the sound channel of the left channel signals of the stereophonic signal that receives and right-channel signals or according to other parameter that receives or information calculations the first weighting factor and the second weighting factor.CLD or other parameters/information can be provided by scrambler.These other parameters can relevant with left channel signals and right-channel signals (that is, not relevant with CLD) other energy indexes, even can be the weighting factor specific to sound channel.
According to the tenth kind of form of implementation of first aspect, this device can also be with a determinant, the first aftertreatment entity and the second aftertreatment entity.This determinant can determine and will carry out aftertreatment to which or which left channel signals and right-channel signals, can make decision according to the classification indication.The first aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the first weighting factor weighting) to come left channel signals is carried out aftertreatment.The second aftertreatment entity can use the temporal envelope of mixed signal under the decoding that receives (by the second weighting factor weighting) to come right-channel signals is carried out aftertreatment.Determinant can be used
Figure BDA0000110624110000051
Calculate the first weighting factor, use
Figure BDA0000110624110000052
Calculate the second weighting factor, wherein said
c = 10 cld 20 ,
cld = 1 N Σ b = 0 b = N CLD [ b ] , And
CLD [ b ] = 10 log 10 Σ k = k b k b + 1 - 1 X 1 [ k ] X 1 * [ k ] Σ k = k b k b + 1 - 1 X 2 [ k ] X 2 * [ k ] .
Specifically, can in scrambler, extract level difference (CLD) between sound channel from left channel signals and right-channel signals by using following equation:
CLD [ b ] = 10 log 10 Σ k = k b k b + 1 - 1 X 1 [ k ] X 1 * [ k ] Σ k = k b k b + 1 - 1 X 2 [ k ] X 2 * [ k ] - - - ( 1 )
Wherein, k is the frequency window index, and b is band index, and kb is the initial window of frequency band b, and X1 and X2 are respectively the frequency spectrums of L channel and R channel.
In addition, can generate stereo classification indication according to the CLD that in scrambler, monitors.Change very soon if detect between two continuous frames CLD, stereophonic signal can be classified as stereo transient signal.
In addition, if according to the decoded CLD of equation (1) greater than 0, represent that then the energy of L channel is higher than the energy of R channel.Can calculate this device is applied to the monophony temporal envelope demoder weighting factor according to the CLD that receives from scrambler, specific as follows: the mean value that at first calculates CLD
cld = 1 N Σ b = 0 b = N CLD [ b ] - - - ( 2 ) Then calculate c
c = 10 cld 20 - - - ( 3 )
At last, calculate the weighting factor aleft of left channel signals and the weighting factor aright of right-channel signals.
a left = 2 c 1 + c - - - ( 4 )
With
a right = 2 1 + c - - - ( 5 )
Before the temporal envelope from the monophony decode procedure is applied to L channel and R channel, can multiply by the corresponding weighting factor that calculates with the time envelope.
The 11 kind of form of implementation according to first aspect, if the non-transient type of classification indication indication stereophonic signal can be configured to preprocessor and can come left channel signals and right-channel signals are carried out aftertreatment with the respective weight temporal envelope of the lower mixed signal of decoding.
The 12 kind of form of implementation according to first aspect, classification indication indication, if the relation between the energy of the right-channel signals of stereophonic signal and the energy of left channel signals over time situation surpasses predetermined threshold value, then stereophonic signal is stereo transient signal.
The 13 kind of form of implementation according to first aspect, classification indication indication, if level difference between the sound channel between the right-channel signals of stereophonic signal and the left channel signals (CLD) over time situation surpasses predetermined threshold value, then stereophonic signal is stereo transient signal.
According to the 14 kind of form of implementation of first aspect, another indication of classifying, if situation is above predetermined threshold value over time for the energy of lower mixed signal, then lower mixed signal is mixed signal under the transient state.If lower mixed signal is mixed signal under the monophony, the energy of lower mixed signal over time situation surpass in the situation of predetermined threshold value, lower mixed signal can be called again mixed signal under the monophony transient state.
Any form of implementation of first aspect can combine with its any other form of implementation, to form new form of implementation.
According to second aspect, suggestion is used and is applicable to decode by the demoder of low rate encoding system from the lower mixed signal of processing stereo signals; If stereophonic signal is transient signal, if perhaps lower mixed signal and stereophonic signal are transient signals, then this demoder is used for lower mixed signal that decoding receives by audio track and one with one and is used for said apparatus that the lower mixed signal of decoding is carried out aftertreatment.
According to the first form of implementation of second aspect, this demoder can be with a up-converter mixer, and this up-converter mixer is used for generating left channel signals and right-channel signals according to lower mixed signal and with the spatial audio parameter of lower mixed signal correction.
Demoder can be any decoding device.In addition, preprocessor can be any after-treatment device.In addition, up-converter mixer can be any raising frequency mixer device.
These devices (that is, demoder, receiver, preprocessor and up-converter mixer) can be implemented in hardware or software.If said apparatus is to implement, can be embodied in the part of equipment (for example computing machine or processor) or system's (for example computer system) in hardware.If said apparatus is to implement in software, can be embodied in computer program, function, routine, program code and maybe can carries out object.
According to the third aspect, a kind of method for the stereophonic signal of decoding of being processed by the audio frequency coding with low bit ratio system is carried out aftertreatment is used in suggestion.The method is used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, and the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.The method comprises following two steps: receive the left channel signals of stereophonic signal and right-channel signals, just from the lower mixed signal of decoding generate left channel signals and right-channel signals, the decode classification indication of transient type of the temporal envelope of lower mixed signal and indication stereophonic signal; According to the temporal envelope of the lower mixed signal of decoding (being weighted in the mode that depends on the classification indication by corresponding weighting factor) in the middle of left channel signals and the right-channel signals at least one carried out aftertreatment.
According to fourth aspect, provide a kind of in the middle of a plurality of sound channel signals of multi-channel signal at least one carried out the device of aftertreatment, the sound channel signal that accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.This device comprises a receiver and a preprocessor.This receiver can be used for receiving at least one sound channel signal of generating from the lower mixed signal of decoding, the decoded temporal envelope of lower mixed signal and the classification indication of indicating the transient type of at least one sound channel signal, and this classification indication is relevant with at least one sound channel signal.This preprocessor can be used for according to the temporal envelope of the lower mixed signal of decoding (being weighted in the mode that depends on the classification indication by corresponding weighting factor) at least one sound channel signal being carried out aftertreatment.
Can fall the multi-channel signal with two above sound channel signals mixed so that this multi-channel signal can be only by a lower mixed signal indication, and corresponding spatial audio parameter collection can rebuild a plurality of sound channel signals from the mixed signal of this time.The mixed signal of this time is called again mixed signal under the monophony.In other words, for mixed signal under the monophony, can will (give an example) fall with the multi-channel signal of five sound channel signals (that is, front sound channel signal, left channel signals, right-channel signals, left back sound channel signal and right back sound channel signal) that to mix be to mix signal under the monophony.The mixed monophony that is a lower mixed signal is multi-channel signal is fallen in stereophonic signal fall mixed a kind of special circumstances.
But, can be to two above sound channel signals (namely, M＞=2) multi-channel signal falls mixed, so that this multi-channel signal can descend mixed signal indication by two or more (but quantity is usually less than M), and corresponding spatial audio parameter collection can rebuild a plurality of sound channel signals from these lower mixed signals.Each lower mixed signal is derived from least two in the middle of a plurality of sound channel signals of multi-channel signal.If from left-side signal and central signal (for example, be arranged in the front sound channel signal of center between left side and the right side) sound channel signal be used to obtain mixed signal first time, and the sound channel signal from right-side signal and central signal is used to obtain mixed signal second time, so, first and second times mixed signal all is called stereo lower mixed signal, that is, left stereo lower mixed signal and right stereo lower mixed signal.In other words, for lower mixed signal, can will (giving an example) fall with the multi-channel signal of five sound channel signals (that is, front sound channel signal, left channel signals, right-channel signals, left back sound channel signal and right back sound channel signal) that to mix be a stereo lower mixed signal in a left side and the stereo lower mixed signal in the right side.Fall and mixed be not limited only to stereo lower mixed signal for a plurality of lower mixed signals, and can comprise the lower mixed signal of any amount of any multi-channel signal combination producing from multi-channel signal.Therefore, corresponding lower mixed signal can be described as again first time mixing sound road signal, second time mixing sound road signal, and the rest may be inferred, the whole lower mixed signal of the common formation of these lower mixing sound road signals.
According to the first form of implementation of fourth aspect, this device will be for the parametric multi-channel audio demoder.
According to the second form of implementation of fourth aspect, can use with the parameter side information that falls mixed signal correction and generate a plurality of multi-channel signals from the decoded form of lower mixed signal and the mixed form of liter.
The third form of implementation according to fourth aspect, this device also comprise one be used for to determine will in the middle of these sound channel signals which or which carry out aftertreatment determinant, this determinant can be made decision according to the classification indication of the transient type of the corresponding sound channel signal of indication.
According to the 4th kind of form of implementation of fourth aspect, determinant can be used for indicating for each these sound channel signal or the every subset that is at least these sound channel signals receive the classification relevant with corresponding sound channel signal.Therefore, this classification indication can be described as again the classification indication specific to sound channel.
According to the 5th kind of form of implementation of fourth aspect, classification indication indication, if situation is above predetermined threshold value over time for the relation between the energy of sound channel signal and the reference signal, then sound channel is the transient state sound channel.
According to the 6th kind of form of implementation of fourth aspect, classification indication indication, if between the sound channel between corresponding sound channel signal and the reference signal level difference (CLD) over time situation surpass predetermined threshold value, then sound channel is the transient state sound channel.
According to the 7th kind of form of implementation of fourth aspect, reference signal that be used for to determine sound channel classification indication and/or CLD is the signal that falls one of them in the middle of mixed signal, a plurality of sound channel signal or be derived from least one sound channel signal.
Because the classification of sound channel signal indication, classification indication and other coding parameter (for example CLD) of lower mixed signal are determined in coder side, purpose is each sound channel signal of determining the space-time characteristic of multi-channel signal and rebuild multi-channel signal by mixed signal under the monophony in demoder, therefore, the classification indication of sound channel signal, the classification indication of lower mixed signal and other coding parameter be the feature of (before coding) indication original channel signal and the relation between these sound channel signals not only, also indicate the sound channel signal that rebuilds separately feature and the relation between these sound channel signals.
According to the 8th kind of form of implementation of fourth aspect, determinant can receive relevant with corresponding sound channel signal specific to level difference CLDm between the sound channel of sound channel for each these sound channel signals.
The 9th kind of form of implementation according to fourth aspect, this device comprise one be used for to determine will in the middle of these sound channel signals which or which carry out aftertreatment determinant, this determinant can determine whether certain sound channel is carried out aftertreatment according to the classification indication of the transient type of the classification indication of the transient type of indication sound channel signal and the lower mixed signal of indication.
According to the tenth kind of form of implementation of fourth aspect, another indication of classifying, if situation is above predetermined threshold value over time for the energy of lower mixed signal, then lower mixed signal is mixed signal under the transient state.
According to the 11 kind of form of implementation of fourth aspect, determinant can determine, if the lower mixed signal of another classification indication indication is not mixed signal under the transient state, then any sound channel signal is not carried out aftertreatment.
The 12 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, and it is not the transient state sound channel that the classification indication indication specific to sound channel relevant with at least one multi-channel signal has a sound channel at least, then determinant can be configured to can control preprocessor at least one sound channel signal is carried out aftertreatment.
The 13 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and the energy indexes of at least one sound channel signal or other index then can be configured to determinant can control preprocessor at least one sound channel signal is carried out aftertreatment greater than energy indexes or other index of the reference signal of correspondence.
The 14 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and between reference signal and at least one sound channel signal specific to level difference CLDm between the sound channel of sound channel less than predetermined threshold value, then determinant can be configured to can control preprocessor at least one sound channel signal is carried out aftertreatment.
The 15 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and between at least one sound channel signal and the reference signal specific to level difference CLDm between the sound channel of sound channel greater than predetermined threshold value, then determinant can be configured to can control preprocessor at least one sound channel signal is carried out aftertreatment.
The 16 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and the energy indexes of at least one sound channel signal then can be configured to determinant can control preprocessor and at least one sound channel signal do not carried out aftertreatment less than the energy indexes of the reference signal of correspondence.
The 17 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and between reference signal and at least one sound channel signal specific to level difference CLDm between the sound channel of sound channel greater than predetermined threshold value, then determinant can be configured to can control preprocessor and (not use the weighting temporal envelope) at least one sound channel signal is carried out aftertreatment.
The 18 kind of form of implementation according to fourth aspect, if the lower mixed signal of another classification indication indication is mixed signal under the transient state, classification indication indication at least one sound channel signal specific to sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and between at least one sound channel signal and the reference signal specific to level difference CLDm between the sound channel of sound channel less than predetermined threshold value, then determinant can be configured to can control preprocessor and (not use the weighting temporal envelope) at least one sound channel signal is carried out aftertreatment.
The 19 kind of form of implementation according to fourth aspect, determinant can be determined the weighting factor specific to sound channel, will be according to level difference CLDm between the sound channel between at least one sound channel signal that receives and the reference signal, use this weighting factor that the temporal envelope of lower mixed signal is weighted, in order at least one sound channel signal is carried out aftertreatment.
According to the 20 kind of form of implementation of fourth aspect, determinant can be determined the weighting factor am specific to sound channel,
Figure BDA0000110624110000111
Wherein c passes through equation
Figure BDA0000110624110000112
Determine that wherein acldm passes through equation
Figure BDA0000110624110000113
Determine, wherein CLDm[b] pass through equation
CLD m [ b ] = 10 log 10 Σ k = k b k b + 1 - 1 X ref [ k ] X ref * [ k ] Σ k = k b k b + 1 - 1 X m [ k ] X m * [ k ] Determine,
Wherein m is the sound channel index, and k is the frequency window index, and b is band index, and kb is the initial window of frequency band b, and Xref is the frequency spectrum of reference signal, and Xm is the frequency spectrum of each sound channel of multi-channel signal.
According to the 21 kind of form of implementation of fourth aspect, multi-channel signal is stereophonic signal, and this stereophonic signal comprises the first sound channel signal and second sound channel signal.
According to the 22 kind of form of implementation of fourth aspect, multi-channel signal is stereophonic signal, and wherein, the first sound channel signal is the left channel signals of this stereophonic signal, the second sound channel signal be this stereophonic signal right-channel signals, vice versa.
The 23 kind of form of implementation according to fourth aspect, multi-channel signal is stereophonic signal, this stereophonic signal comprises the first sound channel signal and second sound channel signal, and wherein reference signal is the first sound channel signal, second sound channel signal or the lower mixed signal of this stereophonic signal.
Any form of implementation of fourth aspect can combine with its any other form of implementation, to form new form of implementation.
According to the 5th aspect, a kind of demoder for the decoding parametric multichannel audio is provided, this demoder comprises lower mixed demoder, a up-converter mixer and the device according to any form of implementation of fourth aspect.Lower mixed demoder can be used for receiving mixed signal under the coding that represent multi-channel signal, and the lower mixed signal of having encoded of decoding generates the lower mixed signal of decoding.Up-converter mixer can be used for receiving from the lower mixed signal of decoding of lower mixed demoder and with the multichannel parameter of the lower mixed signal correction of decoding, also can be used for generating through rising mixed signal under the mixed decoding---this lower mixed signal formation multi-channel signal.
The first form of implementation according to the 5th aspect, lower mixed demoder also comprises a demultiplexer, this demultiplexer can be used for receiving multiplexed audio signal and extracts encoded lower mixed signal and multichannel parameter from multiplexed audio signal, wherein, the multichannel parameter comprises at least one the classification indication that is applicable at least one sound channel signal.
According to the second form of implementation of the 5th aspect, this demultiplexer can be used for indicating for each sound channel signal extracts specific to the classification of sound channel, the transient type of the corresponding sound channel signal of this classification indication indication.
According to the third form of implementation of the 5th aspect, lower mixed demoder also can be used for mixed classification indication under the lower mixed signal extraction of encoding, transient type and the temporal envelope of the lower mixed signal of this classification indication indication (for example, decoded lower mixed signal).
The 4th kind of form of implementation according to the 5th aspect, for each sound channel signal in the middle of a plurality of sound channel signals, or at least one sound channel signal of the subset of a plurality of sound channel signals, the multichannel parameter comprise one relevant with corresponding sound channel specific to level difference between the sound channel of sound channel.
Any form of implementation of the 5th aspect can combine with its any other form of implementation, to form new form of implementation.
According to the 6th aspect, provide a kind of in the middle of a plurality of sound channel signals of multi-channel signal at least one carried out the method for aftertreatment, the sound channel signal that accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.The method may further comprise the steps: receive the temporal envelope of the lower mixed signal of from least one sound channel signal of lower mixed signal generation of decoding, having decoded and indicate the classification of the transient type of at least one sound channel signal to indicate, this classification indication is relevant with at least one sound channel signal.Temporal envelope (being weighted in the mode that depends on the classification indication by corresponding weighting factor) according to the lower mixed signal of decoding is carried out aftertreatment at least one sound channel signal.The corresponding form of implementation of the 6th aspect has also been described according to the described form of implementation in the 4th and the 5th aspect simultaneously.
According to the 7th aspect, the present invention relates to a kind of computer program, this computer program comprises a kind of program code, when when at least one computing machine moves, this program code be used for to be carried out following methods: be used for method that decoding multi-channel signal is carried out aftertreatment, or be used for the method for the stereophonic signal of decoding of being processed by the audio frequency coding with low bit ratio system being carried out aftertreatment according to any form of implementation of the 3rd or the 6th aspect.
As is known to the person skilled in the art, each device (that is, demoder, receiver, determinant, preprocessor and aftertreatment entity) is functional entity, can implement in hardware, software or the two combination.If said apparatus is to implement, can be embodied in the part of equipment (for example computing machine or processor) or system's (for example computer system) in hardware.If said apparatus is to implement in software, can be embodied in computer program, function, routine, program code and maybe can carries out object.
The stereo form of implementation of the 4th to the 6th aspect has formed a kind of concrete multi-channel encoder/decoding form of implementation, because stereophonic signal includes only two sound channel signals (M=2), be left channel signals and right-channel signals, and multi-channel signal can comprise two or more sound channel signals (M＞=2).
The first stereo form of implementation to the third aspect can be considered to again according to the 4th to the 6th aspect stereo/the further developing of multichannel sterego form of implementation, this stereo form of implementation uses one of them sound channel signal (that is, the left channel signals of stereophonic signal or right-channel signals) to determine the sound channel transient type (rather than using lower mixed signal as the reference signal) of other sound channel signal as the reference signal.First further utilizes such fact to the stereo form of implementation of the third aspect: because stereophonic signal includes only two sound channel signals, therefore, comprise the transient state information (or energy information) with reference to sound channel signal according to one in the middle of these two sound channel signals for another " sound channel transient state classification indication " (and CLDm) that determines.Therefore, stereo transient state classification can be counted as concrete (multi-channel signal) sound channel transient state classification situation, this classification is not only relevant with a sound channel signal, and relevant with two sound channel signals (left channel signals and right-channel signals) of stereophonic signal.
The first form of implementation to the third aspect can also further reduce the required bandwidth of transmission stereo information (especially transient state information and energy information, for example CLD), because only need to transmit a stereo classification indication; And if mixed signal is as the reference signal under using, then the form of implementation of the 4th to the 6th aspect needs two independently sound channel classification indications (being respectively applied to two sound channel signals).
Return the form of implementation of multi-channel signal, if use one of them sound channel signal as the reference signal, then only need to be used for the sound channel transient state classification indication of M-1 sound channel signal (M is the quantity that forms the sound channel signal of multi-channel signal).The transient state classification indication of reference signal itself is implicitly included in the sound channel transient state classification indication of other M-1 sound channel signal, and can be as determining whether the reference sound channel signal is carried out aftertreatment according to first to the stereo coding form of implementation of the third aspect.Correspondingly, can classify according to the classification of one of them M-1 sound channel transient state or according to the lower mixed transient state classified information of lower mixed signal and one of them M-1 sound channel transient state and determine whether the reference sound channel signal is carried out aftertreatment.
In substituting form of implementation, can be as to lower mixed signal, reference signal itself being carried out the transient state classification, that is, similar lower mixed transient state is classified, and do not assess and other signal between relation.
Description of drawings
Will more embodiment of the present invention be described in conjunction with following each figure, wherein:
Fig. 1 has shown an a kind of embodiment of the device for the stereophonic signal of decoding being carried out aftertreatment;
Fig. 2 has shown a kind of the first embodiment of demoder, and this demoder comprises one for the device that the stereophonic signal of decoding is carried out aftertreatment;
Fig. 3 has shown a kind of the first embodiment of the scrambler that can couple together with demoder shown in Figure 2;
Fig. 4 has shown a kind of the first embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment;
Fig. 5 has shown a kind of the second embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment;
Fig. 6 has shown a kind of the second embodiment of the scrambler that can couple together with demoder shown in Figure 7;
Fig. 7 has shown a kind of the second embodiment of demoder, and this demoder comprises one for the device that the stereophonic signal of decoding is carried out aftertreatment;
Fig. 8 has shown a kind of the 3rd embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment;
Fig. 9 has shown that an explanation comprises the diagram of the original stereo signal of a transient state sound channel signal and a normal sound channel signal;
Figure 10 has shown that an explanation can not carry out the diagram of the stereo output signal of aftertreatment;
Figure 11 has shown that two sound channel signals of an explanation can not carry out the diagram of the stereo output signal of aftertreatment;
Figure 12 has shown that one only illustrates and can carry out the diagram of the stereo output signal of aftertreatment to left channel signals (being transient signal);
Figure 13 has shown an a kind of embodiment for decoding multi-channel signal being carried out the device of aftertreatment;
Figure 14 has shown a kind of the 3rd embodiment of demoder, and this demoder comprises that is used for the device that decoding multi-channel signal is carried out aftertreatment;
Figure 15 has shown a kind of the 3rd embodiment of the scrambler that can couple together with demoder shown in Figure 14;
Figure 16 has shown a kind of the first embodiment for decoding multi-channel signal being carried out the method for aftertreatment;
Figure 17 has shown a kind of the second embodiment for decoding multi-channel signal being carried out the method for aftertreatment.
Embodiment
The embodiment of the invention provides a kind of detection method and device of multiple-input, multiple-output signal, the detection method and the device that are used for the multiple-input, multiple-output signal, be used for keeping in the situation of same magnitude at the computation complexity with the Parallel Interference Cancellation method, bit error rate performance is better than the Parallel Interference Cancellation method, and the bit error rate performance that the MIMO signal of contraction carries out demodulation is better than the Parallel Interference Cancellation method.
In Fig. 1, an embodiment who is used for the stereophonic signal of decoding of being processed by the audio frequency coding with low bit ratio system is carried out the device 101 of aftertreatment has been described.Device 101 can be used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, and the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.As mentioned above, encoded and decoded lower mixed signal show as stereophonic signal.
Device 101 comprises a receiver 103 and a preprocessor 105.
Receiver 103 can be used for receiving the left channel signals that generates from the lower mixed signal of decoding and right-channel signals, the decode classification indication of transient type of the temporal envelope of lower mixed signal and indication stereophonic signal.
In addition, preprocessor 105 can be used for according to the weighting temporal envelope of the lower mixed signal of having decoded and classification indication in the middle of left channel signals and the right-channel signals at least one being carried out aftertreatment.Specifically, the classification indication can be controlled and will carry out aftertreatment or two sound channel signals are all carried out aftertreatment which sound channel signal.In addition, the decoded weighting temporal envelope of lower mixed signal can be used as the instrument that carries out aftertreatment for to selected one or two sound channel signal.
Fig. 2 has shown the first embodiment of demoder 201.Demoder 201 comprises that a demultiplexer 203, mono decoder 205, up-converter mixer 207 and one are used for the device 209 that carries out aftertreatment.This comprises a determinant 211, the first aftertreatment entity 213 and the first aftertreatment entity 215 for the device 209 that carries out aftertreatment.
Demultiplexer 203 provides lower mixed signal 217 (for example, lower mixed bit stream 217) and another signal 219 (for example, parameter set 219) that receives, and comprises level difference between sound channel (CLD) and other stereo parameter of possibility.
Mono decoder 205 can be used for receiving lower mixed signal 217 and provides the lower mixed signal 221 of decoding to up-converter mixer 207 and device 209.
Up-converter mixer 207 receives decoded lower mixed signal 221 and CLD signal 219, so that output left channel signals 223 and right-channel signals 225.
The determinant 211 of device 209 can be used for receiving signal 231, and (for example, parameter set 231) comprises the temporal envelope of the lower mixed signal of decoding and indicate the classification of the type of the lower mixed signal of having decoded to indicate.It is transient signal or normal signal that the lower mixed signal of having decoded is indicated in the classification indication.The determinant 211 of device 209 also receives signal 219.
Determinant 211 can be used for determining will in the middle of left channel signals 223 and the right-channel signals 225 which or which carry out aftertreatment.Especially, described determinant 211 can be made decision according to the classification indication of the transient type of indication stereophonic signal.This classification indication can be included in the signal 219.In addition, described determinant 211 can be used for controlling respectively the first aftertreatment entity 213 and the second aftertreatment entity 215 by the first control signal 227 and the second control signal 229.
The first aftertreatment entity 213 can come left channel signals 223 is carried out aftertreatment with the temporal envelope 231 of the lower mixed signal of decoding that receives, and wherein said temporal envelope is by the first weighting factor weighting.
Similarly, described the second aftertreatment entity 215 can come right-channel signals 225 is carried out aftertreatment with the temporal envelope 231 of the lower mixed signal of decoding that receives, and wherein said temporal envelope is by the second weighting factor weighting.
For this reason, determinant 211 can be configured to and calculate the first weighting factor and the second weighting factors according to level difference between the sound channel that receives between the left channel signals of stereophonic signal and the right-channel signals 219.
With reference to Fig. 2, Fig. 3 has shown the first embodiment of the scrambler 301 that can couple together with demoder 201 shown in Figure 2.Scrambler 301 shown in Figure 3 and demoder 201 shown in Figure 2 can couple together by transmission sound channel or any other communication link (for example, wired or wireless communication link).
Scrambler 301 comprises a down mixer 303, a lower mixed transient detector 305, a coding entity 307, an extraction apparatus 309, a detecting device 311 and a multiplexer 313.
Down mixer 303 receives left channel signals 315 and the right-channel signals 317 of stereophonic signal.The lower mixed signal 319 of down mixer 303 outputs, the mixed signal 319 of this time offers lower mixed transient detector 305 and coding entity 307.
Because it is mixed signal under the monophony that down mixer can be fallen left channel signals and right-channel signals mixed, therefore, down mixer 303 can be described as again monophony down mixer 303, and lower mixed transient detector 305 can be described as mixed transient detector under monophony transient detector 305 or the monophony.
Monophony transient detector 305 can detect and mix signal under the monophony is transient signal, can also export the classification indication 325 that mixed signal 319 is transient signal under the instruction sheet sound channel.This monophony transient detector can be assessed the energy of the successive frame of mixed signal under the monophony, can also detect when the energy variation situation of mixed signal under the monophony between two continuous frames surpasses predetermined threshold value, and mixed signal is transient signal under the monophony.
Because (common saying is: lower mixed signal itself) situation (and is classified and the sound channel transient state is classified for described stereo transient state after a while over time can to assess under the monophony mixed signal itself for this detection, then can assess the energy variation situation of left channel signals and right-channel signals), therefore, if satisfy above-mentioned condition, namely, the energy variation situation of mixed signal surpasses predetermined threshold value under the monophony between two continuous frames, then the classification of this transient state is called again the classification of monophony transient state (common saying is: lower mixed transient state classification), mixed signal is called again the monophony transient signal (common saying is: lower mixed transient signal) under the monophony.
Therefore, the classification indication 325 of the transient type of the lower mixed signal (being the output of monophony transient detector 305) of indication (monophony) can be described as again the transient state classification indication of the monophony transient type (that is, mixed signal is the monophony transient signal under the monophony) of mixed signal under monophony transient state classification indication or the instruction sheet sound channel.
The encoded temporal envelope 323 of lower mixed signal 321 (for example, encoded lower mixed bit stream 321) and lower mixed signal of coding entity 307 output.Mixed signal is the monophony transient signal under the monophony if the monophony transient detector detects, and then this coding entity can be used for extracting the temporal envelope of mixed signal under the monophony.This coding entity can be used for (giving an example) whole frame is divided into four subframes, calculates the energy of each subframe, and the energy square root of these four subframes of decoding is to represent the temporal envelope of lower mixed signal.
Extraction apparatus 309 can be used for extracting CLD and other stereo parameter from stereophonic signal.Can be by bit stream 327 transmission from CLD and other stereo parameter that stereophonic signal extracts.
In addition, detecting device 311 can be used for carrying out stereo transient state and detects, and the classification indication 329 of the transient type of output indication stereophonic signal.It can be level difference (CLD) between the sound channel that can calculate for the successive frame of stereophonic signal between left channel signals and the right-channel signals with this detector configurations, and can to detect stereophonic signal under the CLD situation of change of the stereophonic signal between two continuous frames (that is, between the left channel signals and right-channel signals of stereophonic signal) surpasses the situation of predetermined threshold value be transient signal.
Owing to assessing left channel signals and right-channel signals (namely for this detection, two signals) energy relationship over time situation (and for the classification of above-mentioned monophony transient state or after a while described general lower mixed transient state classification, only can assess the energy variation situation of a signal), therefore, if satisfy above-mentioned condition, namely, the CLD situation of change of the stereophonic signal between two continuous frames surpasses predetermined threshold value, then this transient state classification is called again stereo transient state classification, and stereophonic signal is called again stereo transient signal.
Therefore, detecting device 311 can be described as again stereo transient detector, and the classification indication 329 of the transient type of indication stereophonic signal can be described as the classification indication of the stereo transient type (that is, the indication stereophonic signal is transient signal) of stereo transient state classification indication or indication stereophonic signal.
Fig. 4 has shown a kind of the first embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment.The method is used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, and the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.
In step 401, generate left channel signals and right-channel signals from the lower mixed signal of decoding, and receive the temporal envelope of the lower mixed signal of having decoded and indicate the classification of the transient type of stereophonic signal to indicate.
In step 403, according to the temporal envelope of the lower mixed signal of decoding (being weighted in the mode that depends on the classification indication by corresponding weighting factor) in the middle of left channel signals and the right-channel signals at least one carried out aftertreatment.
In addition, Fig. 5 has shown a kind of the second embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment.The method is used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, and the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.
In step 501, can check that the lower mixed signal of having decoded is transient signal.
Lower mixed signal is not transient signal if decoded, then only can updating memory in step 503, can service time envelope left channel signals and right-channel signals are carried out aftertreatment.Owing to be mixed signal transient signal normally under the monophony in the situation of transient signal in the middle of left channel signals and the right-channel signals one or two, therefore, can make following hypothesis: if the lower mixed signal of classification indication indication of the transient type of the lower mixed signal of indication is not transient signal, namely, mixed signal is not the monophony transient signal under the monophony, so, left channel signals and right-channel signals are not transient signals, thereby need not to carry out aftertreatment.
Lower mixed signal is transient signal if decoded, and then follows execution in step 505.In step 505, can check that stereophonic signal is transient signal.
If stereophonic signal is not transient signal, in step 507, can use the reinforcement temporal envelope of mixing signal under having decoded that two sound channel signals are all carried out aftertreatment.Stereo transient state classification indication can be counted as an index, and whether whether the situation of change that is used to indicate left channel signals and right-channel signals different (that is, their progresses in time difference).Owing to (for example can assess the situation of change of the relation between left channel signals and the right-channel signals; according to CLD); therefore; if one of them in the middle of these two signals is transient signal; perhaps these two signals all are transient signals but the form of expression is not identical or dissimilar; for example, the energy of left channel signals and right-channel signals is with different trend (increase or reduce) or press different quantitative changes, and then signal can be classified as stereo transient signal usually.Stereophonic signal is classified as the required difference degree of stereo transient signal depend on used index (for example energy) and predetermined threshold value.In view of foregoing, if lower mixed signal is monophony transient signal (seeing step 501), and stereophonic signal is not stereo transient signal, can suppose that then left channel signals and right-channel signals are similar transient signals.Therefore, can use corresponding weighting temporal envelope that these two sound channel signals are carried out aftertreatment, to improve the quality of these two signals.
If stereophonic signal is transient signal, then follow execution in step 509.In view of the explanation that provides for step 505 and 507, if lower mixed signal is monophony transient signal (seeing step 501), and stereophonic signal is stereo transient signal, and then can suppose to only have a sound channel signal (left channel signals or right-channel signals) is transient signal.Therefore, only need to use corresponding weighting temporal envelope that a sound channel signal is carried out aftertreatment, to improve the quality of this sound channel signal.Step 509 be used for to determine that in the middle of these two sound channel signals which is the transient signal that will carry out aftertreatment.
In step 509, can check that whether the CLD that decoded is greater than 0.
CLD then follows execution in step 511 greater than 0 if decoded; Otherwise, follow execution in step 513.
In step 511, can use the temporal envelope of the weighting temporal envelope recovery left channel signals of the lower mixed signal of having decoded.The above for example understands how to calculate the weighting factor that is weighted for the temporal envelope to the lower mixed signal of decoding.
In step 513, can use the temporal envelope of the weighting temporal envelope recovery right-channel signals of the lower mixed signal of having decoded.
Refer step 509 to 513, because left channel signals is (to that is to say for the reference signal of calculating CLD, the sound channel signal that is positioned at the molecule position of the equation (1) that defines CLD), therefore, if the energy of left channel signals, has then been decoded CLD greater than the energy of right-channel signals greater than 0.Because therefore the energy of transient signal, can determine that as an index which is the transient state sound channel signal in the middle of these two sound channel signals with CLD usually greater than the energy of non-transient signal.Correspondingly, if the CLD that decoded, can suppose that left channel signals is the transient state sound channel signal greater than 0, and can use corresponding weighting temporal envelope that it is carried out aftertreatment.CLD can suppose that then right-channel signals is the transient state sound channel signal, and can use corresponding weighting temporal envelope that it is carried out aftertreatment less than 0 if decoded.
In other embodiments, right-channel signals can be used as reference signal, and other index can be used for determining that in the middle of these two signals which is transient signal.
Fig. 6 has shown the second embodiment of scrambler 601.Scrambler 601 can couple together with demoder 701 shown in Figure 7.Scrambler 601 can be based on SWB monophony G.722/G.711.1.
Scrambler 601 shown in Figure 6 comprises a down mixer 603, a monophony scrambler 605, an extraction apparatus 607 and a detecting device 609.Extraction apparatus 607 can be used for extracting CLD and other stereo parameter.Detecting device 609 can be used for carrying out stereo transient state and detects.
Monophony scrambler 605 is with a band separator 611, a high-band monophony transient detector 613, a high-band scrambler 615 and a low strap scrambler 617.
In addition, scrambler 601 is with a multiplexer 619.
Down mixer 603 receives left channel signals 621 and right-channel signals 623.Down mixer 603 can generate lower mixed signal 625 from left channel signals and right-channel signals.Lower mixed signal 625 can be input to monophony scrambler 605.
Lower mixed input signal 625 will be divided into a high band signal and a low band signal by band separator 611 (this separation vessel exemplarily is presented as the QMF band separation filter).These two signals are used as respectively the input of low strap scrambler 617 and high-band scrambler 615.
High-band monophony transient detector 613 provides transient state to detect according to the energy of the high-band time signal of successive frame.Can extract the temporal envelope of high band signal, and it is transferred to demoder (seeing Fig. 7) with classified information.
For example, whole frame can be divided into four subframes, and can calculate the energy of each subframe.The square root of the energy of these four subframes of can decoding represents temporal envelope.
By using aforesaid equation to extract CLD from left channel signals and right-channel signals.
In addition, can detect stereo transient signal by stereo transient detector 609.This detection also can be monitored based on CLD.Change very fast or sudden change (for example, change surpass predetermined threshold value) is arranged if detect between two continuous frames CLD, then stereophonic signal can be classified as stereo transient signal.For example, can detect in the following manner.In the first step, in the daily record territory, calculate the CLD sum of all frequency bands.In the first step, the mean value of the CLD sum of the top n frame of calculating.In the 3rd step, the CLD sum of calculating present frame is the difference between the mean value of the CLD sum of top n frame with it.
In the 4th step, the difference and certain threshold value that calculate are made comparisons, to determine that signal is the transient state stereophonic signal.Used threshold value can draw from experiment.
As mentioned above, Fig. 7 has shown the second embodiment of demoder 701, and this demoder can couple together with demoder 601 shown in Figure 6.
Demoder 701 is used for the device 713 that carries out aftertreatment with a demultiplexer 703, SWB mono decoder 705, WB mono decoder 707, the first up-converter mixer 709, the second up-converter mixer 711 and one.
This comprises a determinant 715, the first aftertreatment entity 717 and the second aftertreatment entity 719 for the device 713 that carries out aftertreatment.
In addition, demoder 701 bands are useful on the first quadrature mirror filter (QMF) 721 that output has been decoded and passed through the left channel signals of aftertreatment.
In addition, demoder 701 bands are useful on the second quadrature mirror filter (QMF) 723 that output has been decoded and passed through the right-channel signals of aftertreatment.
Therefore, can rebuild respectively low strap stereophonic signal and high-band stereophonic signal, shown in the output of up-converter mixer 709 and 711, these signals also can be used as the input signal of QMF wave filter 721 and 723, to generate stereo output signal.Especially, stereo post-processing algorithm is only applicable to the high-band demoder.
Fig. 8 has shown a kind of the 3rd embodiment for the stereophonic signal of decoding being carried out the method for aftertreatment.The method is used for following signal is carried out aftertreatment: at least one in the middle of the left channel signals of stereophonic signal and the right-channel signals, and the left channel signals and the right-channel signals that are just being generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.Correspondingly, the explanation that provides with reference to Fig. 5 is suitable for.
In step 801, can check that the lower mixed signal of having decoded is transient signal.Lower mixed signal is not transient signal if decoded, and then only understands updating memory (as shown in step 803), and can not use the weighting temporal envelope that left channel signals and right-channel signals are carried out aftertreatment.
If the stereophonic signal of present frame is transient signal, if perhaps the lower mixed signal of decoding of previous frame is transient signal and previous frame stereophonic signal is transient signal, so, be "Yes" to the answer of the inspection in step 805, carried out.If the answer to the inspection carried out in step 805 is "No", then execution in step 807 then.If the answer to the inspection carried out in step 805 is "Yes", then execution in step 809 then.
In step 807, can use the weighting temporal envelope of the lower mixed signal of having decoded that left channel signals and right-channel signals are carried out aftertreatment, because can suppose that these two sound channel signals all are transient signals.
For the embodiment according to Fig. 8, left channel signals also is used as reference signal (as among Fig. 5), and the CLD that receives according to equation (1) is used for determining that in the middle of these two signals (left channel signals and right-channel signals) which is transient signal.Therefore, in step 809, can check that whether the CLD that decoded is greater than 0.
CLD then follows execution in step 811 greater than 0 if decoded; Otherwise, follow execution in step 813.
In step 811, can use the temporal envelope of the weighting temporal envelope recovery left channel signals of the lower mixed signal of having decoded.The above for example understands how to calculate the weighting factor that is weighted for the temporal envelope to the lower mixed signal of decoding.
In step 813, can use the temporal envelope of the weighting temporal envelope recovery right-channel signals of the lower mixed signal of having decoded.
In short, if the stereophonic signal of present frame is classified as stereo transient signal, if perhaps lower mixed signal is transient signal, and the stereophonic signal of previous frame is classified as stereo transient signal, then may need to make decision according to the CLD that decoded again.Otherwise, may use the weighting monophony temporal envelope of left channel signals and right-channel signals respectively these two sound channel signals to be carried out aftertreatment.
If need to make decision again, can use CLD.The parameter of CLD_dq by name can be used for the energy relationship between definite these two sound channel signals.Can use aforesaid equation (2) this energy relationship to be calculated as the mean value of all high-band CLD.In addition, the CLD of the first high-band can be used as CLD_dq.
If only having a sound channel signal is transient signal, then the energy of this sound channel signal can be greater than the energy of another sound channel signal.Therefore, energy information can be used for determining which sound channel signal is transient signal.
If CLD_dq is positive number, therefore the energy of expression left channel signals can only use weighting monophony temporal envelope that left channel signals is carried out aftertreatment greater than the energy of right-channel signals.If CLD_dq is negative, therefore the energy of expression left channel signals can only use weighting monophony temporal envelope that right-channel signals is carried out aftertreatment less than the energy of right-channel signals.Can use aforesaid equation (4) and (5) to calculate respectively the weighting factor of these two sound channel signals.
Fig. 9 according to performance of the present invention, can eliminate the Pre-echo artifacts with the stereophonic signal of at least one transient signal to performance specification shown in Figure 12.The chart at Fig. 9 to Figure 12 top has shown left channel signals, and the chart of bottom has shown right-channel signals.To this, Fig. 9 has shown that an explanation is with the diagram of the original stereo signal of a transient state sound channel signal (top chart) and a normal sound channel signal (bottom chart), Figure 10 has shown that an explanation can not carry out the diagram of the stereo output signal of aftertreatment, Figure 11 has shown that an explanation meeting all carries out the diagram of the stereo output signal of aftertreatment to two sound channel signals, and Figure 12 has shown that an explanation only can carry out the diagram of the stereo output signal of aftertreatment to left channel signals (being transient signal).
For Figure 10, if the stereophonic signal that rebuilds is not carried out aftertreatment, then in the circle of Figure 10 obvious Pre-echo artifacts may appear.If two sound channel signals are all carried out aftertreatment, then noise (seeing the circle among Figure 11) may appear in right-channel signals.This algorithm can improve this situation by the better temporal envelope that rebuilds that is applicable to these two sound channel signals in various transient signals combination (that is, left channel signals and right-channel signals, only have left channel signals or only have right-channel signals).
In Figure 13, an embodiment who is used for the decoding multi-channel signal of being processed by the audio frequency coding with low bit ratio system is carried out the device 101 ' of aftertreatment has been described.Device 101 ' can be used in the middle of a plurality of sound channel signals of multi-channel signal at least one carried out aftertreatment, and the sound channel signal that accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.As mentioned above, encoded and decoded lower mixed signal show as multi-channel signal.
Device 101 ' comprises a receiver 103 ' and a preprocessor 105 '.
Receiver 103 ' can be used for receiving at least one sound channel signal (sound channel signal that will receive generates from the lower mixed signal of decoding) in the middle of M the sound channel signal of multi-channel signal, the decode temporal envelope of lower mixed signal and the classification indication of indicating the transient type of at least one sound channel signal.
In addition, preprocessor 105 ' can be used for according to weighting temporal envelope and the classification indication of the lower mixed signal of decoding at least one sound channel signal being carried out aftertreatment.The classification indication can be used for control and whether at least one sound channel signal is carried out aftertreatment.In addition, the decoded weighting temporal envelope of lower mixed signal can be used as for the instrument that selected sound channel signal is carried out aftertreatment.
Plural number M is greater than 1, i.e. M＞1.Hereinafter, m is used as an index, is used for certain central sound channel signal of M sound channel signal of explanation.
Can comprise a receiver 103 ' (can be used for receiving some or all sound channel signals of multi-channel signal, each these sound channel signal generates from the lower mixed signal of decoding), decode a temporal envelope of lower mixed signal and the classification indication that is used for each these sound channel signal every subset of these sound channel signals (or be used at least) among another embodiment; Each is specific to the transient type of the corresponding sound channel signal of classification indication indication of sound channel.The preprocessor 105 ' of another embodiment can be used for according to the weighting temporal envelope of the lower mixed signal of having decoded and classification indication in the middle of these sound channel signals at least one being carried out aftertreatment.The classification indication can be used for control which sound channel signal is carried out aftertreatment.
According to another embodiment, this device also comprises a determinant.This determinant can be used for receiving the classification indication, also can be used for indicating the control preprocessor whether to use specific to the weighting temporal envelope of sound channel according to classification at least one sound channel signal is carried out aftertreatment.
According to another embodiment, this device comprises a determinant, whether this determinant can be used for receiving that mixed signal is the classification indication of transient signal under above-mentioned classification indication and the indication, also can be used for controlling preprocessors according to these two classification indications and use specific to the weighting temporal envelope of sound channel at least one sound channel signal is carried out aftertreatment.
In an alternate embodiment, preprocessor 105 ' can be used for receiving the temporal envelope of lower mixed signal and specific to the weighting factor of sound channel of having decoded, and also can be used for by with this temporal envelope with should multiply each other to generate the weighting temporal envelope specific to weighting factor of sound channel.
The embodiment of this preprocessor can include only an aftertreatment entity, and this entity can be used for one, a plurality of or all sound channel signals are carried out aftertreatment.To carry out aftertreatment to which sound channel signal by determinant control.Other embodiment can comprise a plurality of aftertreatment entities, and for example, for each sound channel signal, the aftertreatment entity of one or more special uses can be used for according to the control of determinant a plurality of sound channel signals being carried out aftertreatment.
Figure 14 has shown the 3rd embodiment of demoder 201 ' (that is the demoder that, is used for the parametric multi-channel audio decoding).Demoder 201 ' comprises that lower 205 ', one up-converter mixer 207 ' of mixed demoder of 203 ', one of a demultiplexer and one are for the device 209 ' that carries out aftertreatment.This comprises a determinant 211 ', the first aftertreatment entity 213 ' and the second aftertreatment entity 215 ' for the device 209 ' that carries out aftertreatment.
Demultiplexer 203 ' can be used for receiving the multiplexed audio signal that comprises lower mixed signal and multichannel parameter, also can be used for minute exporting the lower mixed signal 217 ' (for example lower mixed bit stream 217 ') that receives and the multi-channel audio coding parameter 219 ' relevant with the lower mixed signal 217 ' that receives with the signal (for example bit stream) that receives.These multi-channel audio coding parameters comprise for level difference (CLD) between the sound channel of each sound channel signal of the multi-channel signal of following mixed signal indication, hereinafter, represent with CLDm specific to level difference between the sound channel of sound channel, wherein, m represents to be used to indicate one the central sound channel index of M sound channel signal of multi-channel signal.
Lower mixed demoder 205 ' can be used for receiving the lower mixed signal 217 ' of having encoded, and provides the lower mixed signal 221 ' of decoding to up-converter mixer 207 ' with for the device 209 ' that carries out aftertreatment.
Up-converter mixer 207 ' can be used for receiving the lower mixed signal 221 ' and specific to level difference CLDm between the sound channel of sound channel of having decoded, and also can be used for according to the above-mentioned lower mixed signal 221 ' and generate and M the sound channel signal (being represented by two typical reference signals 223 ' and 225 ') of output multi-channel signal specific to level difference CLDm between the sound channel of sound channel of having decoded.Point between the signal wire (quoting by reference number 223 ' and 225 ') expression multi-channel signal can comprise more than M=2 sound channel signal.
The determinant 211 ' of device 209 ' can be used for receiving signal 231 ', comprises the temporal envelope of the lower mixed signal of decoding and indicates the classification of the transient type of the lower mixed signal of having decoded to indicate.It is transient signal or normal signal (that is, non-transient signal) that the lower mixed signal of having decoded is indicated in the classification indication.Device 209 ' determinant 211 ' also can be used for receiving specific to the CLDm of sound channel with specific to the classified information (seeing signal 219) of sound channel.
Determinant 211 ' can be used for determining will to this M sound channel signal (being respectively 223 ' and 225) central which or which carry out aftertreatment.In other words, determinant 211 ' can be used for decision and whether any sound channel signal is not carried out aftertreatment, whether M sound channel signal is all carried out aftertreatment, and perhaps whether a subset to sound channel signal carries out aftertreatment.Determinant 211 ' can be used for determining that according to the classification indication of the transient type of each sound channel signal of indication this sound channel signal is transient signal or normal signal.This classification indication can be included in the signal 219 '.In addition, determinant 211 ' can be used for by corresponding control signal control aftertreatment entity 213 ' and 215 '.In Figure 14, the control signal 227 ' that is used for control aftertreatment entity 213 ' and the control signal 229 ' that is used for controlling aftertreatment entity 215 ' have been shown.Aftertreatment entity 213 ' can use the temporal envelope 231 ' of the lower mixed signal of decoding that receives to come sound channel signal 223 ' is carried out aftertreatment, and wherein said temporal envelope is by the weighting factor weighting specific to sound channel relevant with sound channel signal 223 '.
Similarly, aftertreatment entity 215 ' can use the temporal envelope 231 ' of the lower mixed signal of decoding that receives to come sound channel signal 225 ' is carried out aftertreatment, and wherein said temporal envelope is by the weighting factor weighting specific to sound channel relevant with this sound channel signal.
Determinant 211 ' can be used for calculating or determining the weighting factor relevant with sound channel signal 223 ' and the weighting factor of being correlated with sound channel signal 225 ' according to level difference CLDm 219 ' between the corresponding sound channel that receives.
For Figure 14, an audio coder the 3rd embodiment of (for example, parametric multi-channel audio scrambler 301 ' is used for providing the multi-channel audio signal of having encoded to decode for demoder shown in Figure 14) has been provided Figure 15.Scrambler 201 ' shown in Figure 14 can pass through transmission link (for example, wired or wireless communication link) and be connected to scrambler 301 ' shown in Figure 15.
Scrambler 301 ' comprises a down mixer 303 ', a lower mixed transient detector 305 ', a coding entity 307 ', an extraction apparatus 309 ', a detecting device 311 ' and a multiplexer 313 '.
Down mixer 303 ' receives M sound channel signal of multi-channel signal.For the sake of simplicity, Figure 15 has only shown central two the representative sound channel signals (being respectively sound channel signal 315 ' and 317 ') of M sound channel signal.Down mixer 303 ' also can be used for generating and the lower mixed signal 319 ' of output, and lower mixed signal 319 ' will be provided for lower mixed transient detector 305 ' and lower shuffling code entity 307 '.Alternatively, determine level difference (CLD) between the sound channel of the sound channel transient state classification of sound channel signal and/or sound channel signal if lower mixed signal is used as reference signal, so, lower mixed signal can also be offered extraction apparatus 309 ' and detecting device 311 '.
It is transient signal that lower mixed transient detector 305 ' can detect lower mixed signal, can also export the classification indication 325 ' that mixed signal 319 ' is transient signal under the indication.The mixed transient detector of this time can be assessed the energy of the successive frame of lower mixed signal, can also detect when the energy variation situation of the lower mixed signal between two continuous frames surpasses predetermined threshold value, and lower mixed signal is transient signal.
Since for this detection can assess lower mixed signal itself over time situation (and for above-mentioned stereo transient state classification or after a while described sound channel transient state classification, only can assess the energy variation situation of two signals), therefore, if satisfy above-mentioned condition, namely, the energy variation situation of the lower mixed signal between two continuous frames surpasses predetermined threshold value, and then this transient state classification is called again lower mixed transient state classification, and lower mixed signal is called again lower mixed transient signal.
Therefore, the classification indication 325 ' of the transient type of the lower mixed signal of indication (by lower mixed transient detector 305 ' output) can be described as again the transient state classification indication of the lower mixed transient type (that is, lower mixed signal whether lower mixed transient signal) of lower mixed transient state classification indication or the lower mixed signal of indication.
Can output have the encoded temporal envelope 323 ' of lower mixed signal 321 ' and lower mixed the signal part of lower mixed signal 321 ' (for example, as) of coding entity 307 '.Only detecting lower mixed signal at lower mixed transient detector is in the situation of lower mixed transient signal, and coding entity 307 ' just can be used for extracting the temporal envelope of lower mixed signal.This coding entity can be used for (giving an example) whole frame is divided into four subframes, calculates the energy of each subframe, and the energy square root of these four subframes of decoding is to represent the temporal envelope of lower mixed signal.
Whether lower mixed transient detector 305 ' can output category indication 325 ', and the lower mixed signal of this classification indication indication 319 ' is lower mixed transient signal, and in other words, the lower mixed signal 319 ' of indication is transient signal or normal signal.As temporal envelope 323 ', classification indication 305 ' can send to demoder with lower mixed signal the part of lower mixed signal (for example, as).
Extraction apparatus 309 ' can be used for receiving M sound channel signal of multi-channel signal, and is that each sound channel signal m of multi-channel signal extracts specific to level difference CLDm between the sound channel of sound channel and other multi-channel audio coding parameter from multi-channel signal.The CLDm that extracts from multi-channel signal and other multi-channel audio coding parameter will be used as side information and be transferred to demoder by signal 327 '.
Detecting device 311 ' can be used for receiving M sound channel signal of multi-channel signal, for providing the sound channel transient state, each sound channel signal detects, and the classification indication 329 ' specific to sound channel of indicating the transient type of corresponding sound channel signal for each sound channel signal output.
If the CLD relevant with sound channel signal m (for example between two continuous frames, the CLD that calculates between sound channel signal m and certain reference signal) situation of change surpasses predetermined threshold value, so, detecting device 311 ' can be used for calculating level difference CLDm between sound channel for each sound channel signal m of the successive frame of multichannel, and also can be used for detecting sound channel signal m is transient signal.This reference signal can be lower mixed signal, any one sound channel signal of multi-channel signal or any other signal that is derived from least one sound channel signal (the extra lower mixed signal that for example, generates from certain subset of sound channel signal).
Owing to assessing actual sound channel signal m and reference signal (namely for this detection, two signals) energy relationship between over time situation (and is classified for above-mentioned lower mixed transient state classification and monophony transient state, then only can assess the energy variation situation of a sound channel signal), therefore, the classification of this transient state is called again the classification of sound channel transient state, makes a distinction in order to classify with monophony or lower mixed transient state classification and stereo transient state.Correspondingly, if satisfy above-mentioned condition, that is, the situation of change of the CLDm relevant with sound channel signal m surpasses predetermined threshold value between two continuous frames, and sound channel signal is called again the sound channel transient signal.
Therefore, detecting device 311 can be described as again the sound channel transient detector, and the classification indication 329 of the transient type of indication sound channel signal can be described as the classification indication of the sound channel transient type (that is, the indication sound channel signal is transient signal) of sound channel transient state classification indication or indication sound channel signal.
According to an embodiment, lower mixed transient detector 305 ' can be used for control (seeing the arrow between 305 ' to 307 ') coding entity 307 ', so that this coding entity temporal envelope 323 ' of mixed signal under just definite in the lower mixed transient detector 305 ' situation that to detect lower mixed signal be lower mixed transient signal only.
In alternate embodiment, coding entity 307 ' can be used for determining temporal envelope 323 ', is lower mixed transient signal and whether detect lower mixed signal regardless of lower mixed transient detector.
Figure 14 and Figure 15 have shown the embodiment that is used for shuffling code under the monophony.Therefore, scrambler (Figure 15) comprises under a monophony down mixer 303 ' (being used for falling a plurality of sound channel signals mixed is mixed signal 319 ' under the monophony), the monophony shuffling code entity 307 ' (being used for mixed signal 319 ' under the encoding mono) and monophony transient detector 305 ' (be monophony transient signal for detection of mixing signal under the monophony).Correspondingly, demoder (Figure 14) comprises under the monophony mixed demoder 205 ' (being used for mixed signal 205 ' under the encoding mono that decoding receives) and monophony up-converter mixer 207 ' (be used for from one M sound channel signal 213 ' and 215 ' of mixed signal 221 ' generation under the decoding mono).
The alternate embodiment of above-mentioned encoder can be used for carrying out many lower mixed or stereo lower shuffling codes, for example, can be used for certain multi-channel signal is fallen mixed, so that this multi-channel signal can descend mixed signal indication by two or more (but quantity is usually less than M), and corresponding spatial audio parameter energy collecting enough rebuilds the sound channel signal from a plurality of lower mixed signals.Each lower mixed signal is derived from least two in the middle of a plurality of sound channel signals of multi-channel signal.In this type of embodiment, scrambler comprises a down mixer (being used for mixed two or more lower mixed signals that are are fallen in a plurality of sound channel signals), one or more lower shuffling code entity (being used for the lower mixed signal of coding) and one or more lower mixed transient detector (for detection of at least one lower mixed signal lower mixed transient signal whether).Correspondingly, demoder comprises one or more lower mixed demoders (mixed signal under the coding that receives that is used for decoding), a up-converter mixer 207 ' (being used for generating M sound channel signals 213 ' and 215 ' from two or more lower mixed signals of having decoded) and a determinant (whether being classified as lower mixed transient signal for assessment of at least one lower mixed signal).
Figure 16 has shown the process flow diagram of a kind of the first embodiment of the method for decoding multi-channel signal being carried out aftertreatment.This post-processing approach can be used in the middle of a plurality of sound channel signals of multi-channel signal at least one carried out aftertreatment, and the sound channel signal that accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.As mentioned above, encoded and decoded lower mixed signal show as multi-channel signal.The method may further comprise the steps:
At least one sound channel signal that reception generates from the lower mixed signal of decoding, the decode temporal envelope of lower mixed signal and the classification indication of indicating the transient type of at least one sound channel signal, this classification indication relevant with at least one sound channel signal (step 401 ').
According to the temporal envelope of the lower mixed signal of decoding (being weighted in the mode that depends on the classification indication by corresponding weighting factor) at least one sound channel signal is carried out aftertreatment (step 403 ').
Figure 17 has shown the process flow diagram of a kind of the second embodiment of the method for decoding multi-channel signal being carried out aftertreatment, and wherein said lower mixed signal is used as reference signal.This post-processing approach can be used in the middle of a plurality of sound channel signals of multi-channel signal at least one carried out aftertreatment, and the sound channel signal that accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system.As mentioned above, encoded and decoded lower mixed signal show as multi-channel signal.The method may further comprise the steps:
In step 501 ' in, can check that lower mixed signal is transient signal.
If lower mixed signal is not transient signal, then in step 503 ' in only can updating memory, and can not use the weighting temporal envelope specific to sound channel of lower mixed signal that any multi-channel signal is carried out aftertreatment.Because at least one sound channel signal of the multi-channel signal of mixed signal is in the situation of transient signal under generating, lower mixed signal is transient signal normally, therefore, can make following hypothesis: if the lower mixed signal of classification indication indication of the transient type of the lower mixed signal of indication is not transient signal, that is, lower mixed signal is not lower mixed transient signal, so, any one sound channel signal is not transient signal, thereby need not to carry out aftertreatment.
Lower mixed signal is transient signal if decoded, and then follows execution in step 505 '.In step 505 ' in, can check that sound channel signal m is transient signal.No matter whether the situation of change of sound channel signal m is identical with the situation of change of reference signal, that is to say, no matter whether sound channel signal m is identical with reference signal progress in time, can see sound channel transient state classification indication as an index.Owing to (for example can assess the situation of change of the relation between sound channel signal m and the reference signal; according to CLD); therefore; if one of them in the middle of these two signals is transient signal; perhaps these two signals all are transient signals but the form of expression is not identical or dissimilar; for example, the energy of sound channel signal m and reference signal is with different trend (increase or reduce) or press different quantitative changes, and then signal can be classified as the sound channel transient signal usually.Sound channel signal is classified as the required difference degree of sound channel transient signal depend on used index (for example energy) and predetermined threshold value.In view of foregoing, if lower mixed signal is classified as lower mixed transient signal (seeing step 501), and sound channel signal is not the sound channel transient signal, can suppose that then sound channel signal m and reference signal are similar transient signals.
Therefore, if sound channel signal m is not the sound channel transient signal, then follows execution in step 507 ', and can use the temporal envelope (being weighted by the weighting factor specific to sound channel) of lower mixed signal that sound channel signal m is carried out aftertreatment.
If sound channel signal m is transient signal, then follow execution in step 509 '.In step 509 ' in, can check for sound channel signal m specific to the CLDm of sound channel whether greater than 0.
If specific to the CLDm of sound channel greater than 0, then execution in step 511 ' then.Otherwise, follow execution in step 513 '.
In step 511 ' in, can not carry out aftertreatment to multi-channel signal m, that is to say, can not use weighting sound channel temporal envelope that sound channel signal m is carried out aftertreatment.
In step 513 ' in, can be by using the temporal envelope that specific to the weighting factor of sound channel the temporal envelope of lower mixed signal is weighted to recover or rebuild sound channel signal m.
Refer step 509 ' to 513 ', owing to be (to that is to say for the reference signal of calculating CLD with reference to sound channel signal, the sound channel signal that is positioned at the molecule position of the equation (5) that defines CLDm), therefore, if the energy of reference signal, has then been decoded CLDm greater than the energy of sound channel signal m greater than 0.Because therefore the energy of transient signal, can determine as an index whether sound channel signal m can be looked at as transient signal with respect to reference signal with CLDm usually greater than the energy of non-transient signal.Correspondingly, if the CLDm that decoded, can suppose that sound channel signal m is not transient signal with respect to reference signal greater than 0, and can not use corresponding weighting temporal envelope that sound channel signal m is carried out aftertreatment (see step 511 ').CLDm can suppose then that less than 0 sound channel signal m is transient signal with respect to reference signal if decoded, and can use corresponding weighting temporal envelope that sound channel signal m is carried out aftertreatment (see step 513 ').
In an alternate embodiment, one of them sound channel signal is used as reference signal.Can be used for multi-channel signal is carried out aftertreatment according to the described method of Figure 16.In the case, only need M-1 sound channel transient state classification indication to determine whether and to carry out aftertreatment to M sound channel signal.Can use the sort of method or the similar approach introduced for stereo coding (according to Fig. 5 and Fig. 8) to determine whether the reference sound channel signal is carried out aftertreatment.
In another alternate embodiment, whole lower mixed signal is comprised of a plurality of (more than or equal to 1 but less than M) lower mixed signal.In the case, reference signal can be one of them lower mixed signal, and the lower mixed signal of indication is the lower mixed transient state indication and the mixed signal correction of this time of transient signal.
With reference to Figure 15,14 and 17, can carry out in such a way multi-channel audio coding and decoding.
At first, in scrambler, (see Figure 15), generate lower mixed signal from M the sound channel signal (C1 to CM is corresponding to reference signal 315 ' to 317 ') that forms multi-channel signal, and will descend mixed signal as the input of lower mixed scrambler 307 '.In the lower mixed scrambler transient state detection model is arranged.If lower mixed signal 319 ' is classified as lower mixed transient signal, lower mixed scrambler 307 ' will extract the temporal envelope 323 ' of the mixed signal of this time, and this temporal envelope will be transferred to demoder.
Extraction apparatus 309 ' is by using following equation to extract CLD from multi-channel signal:
CLD m [ b ] = 10 log 10 Σ k = k b k b + 1 - 1 X ref [ k ] X ref * [ f ] Σ k = k b k b + 1 - 1 X m [ k ] X m * [ k ] - - - ( 1 ) ,
Wherein, k is the frequency window index, and b is band index, and kb is the initial window of frequency band b, and Xref is the frequency spectrum of reference signal, and Xm is the frequency spectrum of each sound channel of multi-channel signal.The frequency spectrum Xref of reference signal can be the frequency spectrum of lower mixed signal D 319 ', also can be the frequency spectrum Xm (for the m in [1, M]) of one of them sound channel signal.
Also need to detect the sound channel transient signal.This detection (is given an example) take the CLDm monitoring as foundation, is carried out by detecting device 311 '.Change very fast (this situation is called again sudden change) if detect two CLDm between the continuous frame, then sound channel signal m will be classified as the sound channel transient signal.
In demoder, (see Figure 14), can be with decoding lower mixed signal and rebuild multi-channel signal with the multichannel parameter of the mixed signal correction of this time.
If the classification indication that receives from the lower mixed signal of decoding is lower mixed transient state classification indication, then embodiments of the invention can improve with the extra process module quality of transient state multi-channel signal.
Figure 16 has illustrated an embodiment of the coding/decoding method of being carried out by demoder shown in Figure 14, and CLD_dqm＞0 of having decoded (see step 509 ') expression is with reference to the energy of the sound channel signal energy greater than the sound channel signal m in the research.
The weighting factor that is applied to the lower envelope of doing time of lower mixed signal is calculated in such a way by determinant 211 '.At first calculate the mean value of CLDm
acld m = 1 N Σ b = 0 b = N CLD m [ b ] - - - ( 2 ) .
Then calculate c
c = 10 acld m 20 - - - ( 3 ) .
At last, calculate the weighting factor of sound channel signal m by following equation:
a m = 2 1 + c - - - ( 4 )
Before will being applied to sound channel signal m from the temporal envelope that lower mixed decode procedure obtains, can multiply by corresponding weighting factor am with this temporal envelope first.
Can or be that in the middle of a plurality of sound channel signals one or some are carried out following operation for each sound channel signal, and can simultaneously or carry out continuously these operations: determine that sound channel signal m is the sound channel transient signal; Calculating is specific to the weighting factor am of sound channel; Generate weighting temporal envelope specific to sound channel according to the temporal envelope of lower mixed signal with specific to the weighting factor am of sound channel; And according to specific to the temporal envelope of sound channel sound channel signal being carried out aftertreatment (as introducing for the multi-channel signal coding).
Although by the agency of main embodiment, wherein, all M of multi-channel signal (or M-1, if a sound channel signal is used as reference signal) sound channel signal is classified as the sound channel transient signal, but still can implement other embodiment and the corresponding method of scrambler, device and demoder, in order to only a subset of M sound channel signal carried out Code And Decode, perhaps sound channel signal classified and aftertreatment.Please note, can be as the same wherein two sound channel signals of processing the multi-channel signal that comprises M＞2 sound channel signal with right-channel signals of left channel signals of processing stereophonic signal, so that can be to the embodiment of the stereo processing of these signal application (for example, with stereo transient state classification or the classification of sound channel transient state).

Claims (19)

1. install (101,201,713; 101 '; 201 ') be used at least one sound channel signal in the middle of a plurality of sound channel signals of multi-channel signal is carried out aftertreatment, described at least one sound channel signal that wherein will accept aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system, this device (101,201,713; 101 '; 201 ') comprising:
Receiver (103; 103 '), be used for to receive at least one sound channel signal of generating from the lower mixed signal of decoding, the decoded temporal envelope of lower mixed signal and the classification indication of indicating the transient type of at least one sound channel signal, this classification indication is relevant with at least one sound channel signal; And
Preprocessor (105,213,215,717,719; 105 ', 213 ', 215 '), be used for according to the temporal envelope of the lower mixed signal of decoding at least one sound channel signal being carried out aftertreatment, described temporal envelope is weighted through the weighting factor that the method based on the classification indication produces.
2. device according to claim 1, wherein said receiver (103; 103 ') be used for receiving a plurality of sound channel signals and a plurality of classification indication, wherein each classification indication is relevant with the sound channel signal of described sound channel signal, and the transient type of each relevant sound channel signal of indication indication of classifying; This device also comprises:
Determinant (211; 715; 211 '), for the sound channel signal of determining to carry out aftertreatment in the middle of described a plurality of sound channel signals, wherein said determinant is determined according to the classification indication of the transient type of the corresponding sound channel signal of indication.
3. device according to claim 1 and 2, this device comprise for the determinant (211 of determining to carry out in the middle of described a plurality of sound channel signals the sound channel signal of aftertreatment; 715; 211 '), this determinant can indicate and indicate the classification indication of the transient type of lower mixed signal to determine according to the classification of the transient type of indicating sound channel signal.
4. device according to claim 3, if the lower mixed signal of classification indication indication is mixed signal under the transient state, and it is not the transient state sound channel that the classification of the sound channel relevant with at least one multi-channel signal indication indication has a sound channel at least, then wherein said determinant (211 ') can be configured to control preprocessor at least one sound channel signal is carried out aftertreatment.
5. according to claim 3 or 4 described devices, if the lower mixed signal of classification indication indication is mixed signal under the transient state, at least one sound channel signal of classification indication indication of the sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and the energy indexes of at least one sound channel signal is greater than the energy indexes of the reference signal of correspondence, and then described determinant (211 ') is configured to control preprocessor at least one sound channel signal is carried out aftertreatment.
6. any described device in 5 according to claim 3, if the lower mixed signal of classification indication indication is mixed signal under the transient state, at least one sound channel signal of classification indication indication of the sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and level difference CLDm is less than predetermined threshold value between the sound channel of the sound channel between reference signal and at least one sound channel signal, and then described determinant (211 ') is configured to control preprocessor at least one sound channel signal is carried out aftertreatment.
7. any described device in 6 according to claim 3, if the lower mixed signal of classification indication indication is mixed signal under the transient state, at least one sound channel signal of classification indication indication of the sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and the energy indexes of at least one sound channel signal is less than the energy indexes of the reference signal of correspondence, and then described determinant (211 ') is configured to control preprocessor and at least one sound channel signal is not carried out aftertreatment.
8. any described device in 7 according to claim 3, if the lower mixed signal of classification indication indication is mixed signal under the transient state, at least one sound channel signal of classification indication indication of the sound channel relevant with at least one multi-channel signal is the transient state sound channel signal, and level difference CLDm is greater than predetermined threshold value between the sound channel of the sound channel between reference signal and at least one sound channel signal, and then described determinant (211 ') is configured to and can at least one sound channel signal not be carried out aftertreatment by using weighting temporal envelope control preprocessor.
9. any described device in 8 according to claim 3, wherein said determinant (211 ') is used for determining weighting factor, according to level difference CLDm between the sound channel between at least one sound channel signal that receives and the reference signal, use this weighting factor that the temporal envelope of lower mixed signal is weighted, in order at least one sound channel signal is carried out aftertreatment.
10. any described device in 9 according to claim 1, wherein said lower mixed signal formation reference signal.
11. any described device in 10 according to claim 1, wherein said multi-channel signal is stereophonic signal, and this stereophonic signal comprises the first sound channel signal and second sound channel signal.
12. demoder (201 ') that is used for carrying out the multichannel audio decoding, this demoder comprises lower mixed decoding signals (205 '), upper mixed device (207 ') and any one described device (209 ') in the middle of 11 according to claim 1, wherein, lower mixed decoding signals (205 ') is used for receiving mixed signal under the coding that represents multi-channel signal, and decoding has been encoded lower mixed signal to generate the lower mixed signal of having decoded, upper mixed device (207 ') be used for receiving from the lower mixed signal of decoding of lower mixed decoding signals (205 ') and with the multichannel parameter of the mixed signal correction of this time, and a plurality of sound channel signals that mix to generate multi-channel signal on according to the multichannel parameter that receives the lower mixed signal of decoding being carried out.
13. one kind for the method that at least one sound channel signal in the middle of a plurality of sound channel signals of multi-channel signal is carried out aftertreatment, the wherein said sound channel signal that carries out aftertreatment is generated from the lower mixed signal of decoding by audio frequency coding with low bit ratio/decode system, and the method may further comprise the steps:
At least one sound channel signal that reception generates from the lower mixed signal of decoding, the decode temporal envelope of lower mixed signal and the classification indication of indicating the transient type of at least one sound channel signal, the relevant (step 401 with at least one sound channel signal of this classification indication; 401 '); And
Temporal envelope according to the lower mixed signal of decoding is carried out aftertreatment at least one sound channel signal, and described temporal envelope is weighted (step 403 through the weighting factor that the method based on the classification indication generates; 403 ').
14. device (101,201,713), this device is used for the left channel signals of stereophonic signal and at least one in the middle of the right-channel signals carried out aftertreatment, wherein generates described left channel signals and right-channel signals by audio frequency coding with low bit ratio/decode system from the lower mixed signal of decoding; This device (101,201,713) comprising:
Receiver (103) be used for to receive the described left channel signals that generates from the lower mixed signal of decoding and right-channel signals, the decode classification indication of transient type of the temporal envelope of lower mixed signal and indication stereophonic signal; And
Preprocessor (105,213,215,717,719), be used for according to the temporal envelope of the described lower mixed signal of having decoded in the middle of described left channel signals and the right-channel signals at least one being carried out aftertreatment, described temporal envelope is weighted through the weighting factor based on the method for classification indication.
15. device according to claim 14 also comprises determinant (211,715), this determinant is used for indicating the sound channel signal that carries out aftertreatment in the middle of definite described a plurality of sound channel signals according to the classification of the transient type of indication stereophonic signal.
16. according to claim 14 or 15 described devices also comprise determinant (211,715), this determinant is wherein indicated and is indicated the classification of the transient type of the lower mixed signal of having decoded to indicate according to the classification of the transient type of indicating stereophonic signal and determine for the sound channel signal of determining to carry out aftertreatment in the middle of described left channel signals and the right-channel signals.
17. one is used for decoding by the demoder of audio frequency coding with low bit ratio system from the lower mixed signal of processing stereo signals, this demoder (201,701) comprise that one is used for decoding by the mono decoder (205 of the lower mixed signal of audio track reception, 705), and one be used for device (213,215,717 that any described lower mixed signal of having decoded in the middle of 16 are according to claim 14 carried out aftertreatment, 719), wherein said lower mixed signal is transient signal.
18. left channel signals and central at least one of right-channel signals that is used for stereophonic signal carried out the method for aftertreatment, wherein generates described left channel signals and right-channel signals by audio frequency coding with low bit ratio/decode system from the lower mixed signal of decoding; The method comprises:
The left channel signals that reception generates from the lower mixed signal of decoding and right-channel signals, the decode classification indication (step 401) of transient type of the temporal envelope of lower mixed signal and indication stereophonic signal; And
According to the temporal envelope of the lower mixed signal of decoding in the middle of left channel signals and the right-channel signals at least one carried out aftertreatment (step 403), described temporal envelope is weighted through the weighting factor that the method based on the classification indication produces.
19. a computer program, when moving on computers, this program can be used for executive basis claim 13 or 18 described methods.
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